1. Field of the Invention
The present invention relates to an optical waveguide and an optical touch panel using the same.
2. Description of the Related Art
An optical touch panel using optical waveguides each having a plurality of cores and a cladding surrounding the cores has been conventionally known (for example, U.S. Pat. No. 5,914,709). Such an optical touch panel determines the coordinates of position of a finger or a pen blocking a grid of light beams (infrared light beams), which is formed over a display screen with the use of optical waveguides, by detecting the intensity of light beams blocked by the finger or pen. Further, an optical touch panel using optical waveguides is thin and highly sensitive, and is therefore expected to have great potential.
However, an optical touch panel using conventional optical waveguides has drawbacks in that it is difficult to perform the positioning of the optical waveguides and that it is also difficult to reduce the width of a frame thereof because the optical waveguides are arranged around a display screen.
FIG. 1 shows plan and sectional views of a main part of an optical touch panel 10 using conventional optical waveguides 13. In the optical touch panel 10 using the conventional optical waveguides 13, the optical waveguides 13 are provided on a frame 12 surrounding a display screen 11.
The two long sides of the rectangular flat plate-shaped optical waveguide 13 have to be parallel to the corresponding long side of the frame 12. However, actually, it is difficult to attach the optical waveguide 13 to the frame 12 so that the two long sides of the rectangular flat plate-shaped optical waveguide 13 becomes parallel to the corresponding long side of the frame 12 during assembly. Therefore, as shown in FIG. 1, misalignment (nonparallel) of the optical waveguide 13 is likely to occur. If such misalignment of the optical waveguide 13 occurs, as shown in FIG. 1, light beams 14 deviate from their normal emission direction, and are therefore not emitted in a direction perpendicular to one side of the rectangular display screen 11 opposed to one long side of the rectangular flat plate-shaped optical waveguide 13, thereby lowering optical transmission efficiency.
Further, in the optical touch panel 10 using the conventional optical waveguides 13, the width of the frame 12 represented by W1 needs to be equal to or larger than that of the optical waveguide 13 represented by W3. This makes it difficult to reduce the width “W1” of the frame 12.